arXiv subjects

Lucien Kuiper

Publications and source records attributed to Lucien Kuiper.

24 records · Page 2Linked to original sources

arXiv2007

New Phase-coherent Measurements of Pulsar Braking Indices

Pulsar braking indices offer insight into the physics that underlies pulsar spin-down. Only five braking indices have been measured via phase-coherent timing; all measured values are less than 3, the value expected from magnetic dipole radiation. Here we present new measurements for three of the five pulsar braking indices, obtained with phase-coherent timing for PSRs J1846-0258 (n=2.65+/-0.01), B1509-58 (n=2.839+/-0.001) and B0540-69 (n=2.140+/-0.009). We discuss the implications of these results and possible physical explanations for them.

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arXiv2006

Supernova remnant energetics and magnetars: no evidence in favour of millisecond proto-neutron stars

It is generally accepted that Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are magnetars, i.e. neutron stars with extremely high surface magnetic fields ($B > 10^{14}$ G). The origin of these high magnetic fields is uncertain, but a popular hypothesis is that magnetars are born with an initial spin period not much exceeding the convective overturn time (~3ms), which results in a powerful dynamo action, amplifying the seed magnetic field to $> ~10^{15}$ G. Part of this rotation energy is then expected to power the supernova through rapid magnetic braking. It is therefore possible that magnetars creation is accompanied by supernovae that are an order of magnitude more energetic than normal supernovae, provided their initial spin period is ~1 ms. However, we list here evidence that the explosion energies of these supernova remnants associated with AXPs and SGRs -- Kes 73 (AXP 1E 1841-045), CTB 109 (AXP 1E2259+586) and N49 (SGR 0526-66) -- are close to the canonical supernova explosion energy of $10^{51}$~erg, suggesting an initial spin period of > ~5ms. We therefore do not find evidence that magnetars are formed from rapidly rotating proto-neutron stars, allowing for the possibility that they descend from stellar progenitor with high magnetic field cores, and we discuss the merits of both formation scenarios. In an appendix we describe the analysis of XMM-Newton observations of Kes 73 and N49 used to derive the explosion energies for these remnants.

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arXiv2006

A Braking Index for the Young, High-Magnetic-Field, Rotation-Powered Pulsar in Kes 75

We present the first phase-coherent measurement of a braking index for the young, energetic rotation-powered pulsar PSR J1846-0258. This 324 ms pulsar is located at the center of the supernova remnant Kes 75 and has a characteristic age of tau_c = 723 years, a spin-down energy of 8.3x10^{36}erg/s, and inferred magnetic field of 4.9x10^{13} G. Two independent phase-coherent timing solutions are derived which together span 5.5 yr of data obtained with the Rossi X-ray Timing Explorer. In addition, a partially phase-coherent timing analysis confirms the fully phase-coherent result. The measured value of the braking index, n=2.65+/-0.01, is significantly less than 3, the value expected from magnetic dipole radiation, implying another physical process must contribute to the pulsar's rotational evolution. Assuming the braking index has been constant since birth, we place an upper limit on the spin-down age of J1846-0258 of 884 yr, the smallest age estimate of any rotation-powered pulsar.

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arXiv2003

PSR B1929+10 revisited in X-ray

We performed timing and spectral analysis for PSR B1929+10, one of the oldest (about 10^7 years) of the ordinary pulsars detected in X-rays, using archival ROSAT, ASCA and RXTE data. Pulsed emission was detected at a more than five sigma level for combined ROSAT PSPC and unpublished HRI data. Our pulse profile is in agreement with that obtained by Yancopoulos et al. (1994; ROSAT PSPC) but now with better statistics. An investigation of the behaviour of the pulsed signal as a function of energy, based on PSPC data, provides indications that the pulsed fraction is changing with energy. The most important new result from this work is derived from the spectral analysis=2E We found that the combined ROSAT PSPC and ASCA GIS spectrum can satisfactorily be described by a power-law as well as by a double black-body model but not by a single black-body model, as was presented earlier by Yancopoulos et al. (1994; ROSAT) and Wang et al. (1997; ASCA). Fitting the combined ROSAT/ASCA 0.1 - 10 keV spectrum by a power-law model we obtain a photon index of 2.54 +/- 0.12 and a neutral Hydrogen column density N_H towards the source of 9.8_{-1.0}^{+1.4} x 10^20 cm^-2. For a double black-body fit our results are: T_1 = 2.0_{-0.05}^{+0.05} x 10^6 K, T_2 = 6.9_{-0.35}^{+0.23} x 10^6 K, and N_H = 4.43_{-1.12}^{+2.08} x 10^20 cm^-2. In both cases the derived N_H value is higher than that adopted in earlier works, but our result is consistent with the larger distance estimate of 331 +/- 10 pc from new parallax measurements performed by Brisken et al. (2002) and with the Hydrogen distribution measured in the direction of the pulsar (Frisch & York, 1983). No significant pulsed signal is found in the RXTE data.

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arXiv2002

Very low luminosities from the accretion-driven millisecond X-ray pulsar SAX J1808.4-3658 during quiescence

We have observed the millisecond X-ray pulsar SAX J1808.4-3658 on three occasions during its 2000 outburst with the BeppoSAX satellite. The source was highly variable and erratic during this outburst, and by coincidence we obtained data only during times when the source had very low luminosities. During our observations, we detected four faint sources. The source closest to the position of SAX J1808.4-3658 is still ~1.6' away. This source can only be identified with SAX J1808.4-3658 if we assume that the BeppoSAX positional reconstruction is not completely understood. We also reanalyzed a BeppoSAX observation taken in March 1999 when the source was in quiescence and during which the source was thought to have been detected (Stella et al. 2000). Based on the similarities (position and luminosity) of this source with the above mentioned source ~1.6' away from SAX J1808.4-3658, it is possible that they are the same source. If this source is not the millisecond pulsar, then during all BeppoSAX observations of SAX J1808.4-3658 (the 2000 outburst ones and the 1999 quiescent one), the millisecond pulsar was not detected. A reanalysis of the ASCA quiescent data of SAX J1808.4-3658 (Dotani, Asai, & Wijnands 2000) confirms that during this observation the source was securely detected in quiescence. We discuss our results for SAX J1808.4-3658 in the context of the quiescent properties of low-mass X-ray binary transients.

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arXiv1997

The Locations of Gamma-Ray Bursts Measured by COMPTEL

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 1.25$\arcdeg$ (1$σ$), including a systematic error of $\sim0.5\arcdeg$, which is verified through comparison with Interplanetary Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements results in locations for 26 of the bursts with an average ``error box'' area of only $\sim$0.3 deg$^2$ (1$σ$). We find that the angular distribution of COMPTEL burst locations is consistent with large-scale isotropy and that there is no statistically significant evidence of small-angle auto-correlations. We conclude that there is no compelling evidence for burst repetition since no more than two of the events (or $\sim$7% of the 29 bursts) could possibly have come from the same source. We also find that there is no significant correlation between the burst locations and either Abell clusters of galaxies or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN annuli places a lower limit of $\sim$100~AU (95% confidence) on the distance to the stronger bursts.

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